F451

Hey guys,

Just reading NJSharkFan's thread about his timing belt tension light reminded me of a question I've been wondering about concerning the different timing belt tension check tools: Kempf vs the special Porsche tool ($$$).

I'm sure this has been covered before, but has anyone looked at the differences in the calibration between the Kempf tool and the spendy Porsche timing belt tension tool when it comes to measuring belt tension on the 32v motors?

One of the reason's that I ask, is that when Earl Gillstrom and I checked the tension on my '88 S4, we used his special Porsche tool and set it at the recommended 5.3 reading (if I'm remembering correctly). Since I had a Kempf tool with me, we decided to see where that would read, and in effect "calibrate" it in a shade tree mechanic sort of way.

My Kempf tool actually read about 1/16" past the highest edge of the gap when the special Porsche tool read 5.3. In other words, when the belt was tensionsed correctly according to the special Porsche tool, on the Kempf tool it read about 1/16" past the "tightest" end of the gap on the Kempf tool.

So, for my Kempf tool, I'm considering it "calibrated", and when I use it in the future on the 32v motors, I'll be setting the tension to about 1/16th inch past the tightest end of the Kempf tool.

Earl also mentioned that the Kempf tool was designed for the 16v motors, but I'm not sure how or why that would impact the reading on a 32v motor, unless the belts are suppossed to be set at a different tension for 16v vs 32v.

And I've been a bit suspicious of the Kempf tool with its simple spring for measuring the belt tension, but it seemed to give accurate and repeatable results when we used it and checked it against the special Porsche tool, so it does seem to work fine.

Anyway, just wondering what others experience has been with the Kempf tool and if anyone else has "calibrated" there's against the special Porsche tool the way Earl and I did.

Ed

Shane

I've always had to set the tension to the tight side of the window on the Kempf tool. If I didn't I would get a warning light every time I stomped on the gas.

RngTrtl

There are going to be differences obviously between the OEM tool and the kempf tool. one is a simple spring/lever assembly and the other is a complex engineered machine. The kempf tool keeps you in a pretty safe window of operation cheaply, the OEM tool keeps you in a very safe window of operation expensively. I am not realy seeing what you are trying to ask or point out.

PorKen

Good to hear. The reading with my automatic tensioner is just above the tight range of the window on my Kempf tool.

I seem to recall others saying that the 32V reading was high on the window.

I wonder if the sensor spring adds to the tension at all. What happens when the sensor spring gets old/tired, or hot for that matter?

F451

I realize that the spendy Porsche tool is going to read more accurately then the simple Kempf tool, but thanks for pointing that out.

To answer your questions, I'll try to clarify.

What I'm seeing: When my belt is tensioned to the correct tension with the special Porsche tool, on the Kempf tool it reads BEYOND the acceptable gap.

What I would like to point out: That depending on how your Kempf tool reads, it 'may' be possible to be setting your belt too lose, and yet still have it read in the allowable range on the Kempf tool.

So, it may be possible (depending on how your Kempf tool reads) to set your belt tension on the loose side if you only use the Kempf tool.

So, I am wondering if others have run into this situation, and if they are taking the difference into consideration.

And judging by Shane's response, it seems like people are taking this into account and when using the Kempf tool, they are setting it to the highest reading (and on mine, it actually has to be set beyond the highest reading to equal the special Porsche tool).

RngTrtl

ahhhh, i gotcha now. You are trying to get the concensus on how others' kempf tool reads in comparison to the porshe tool. I didnt get that in the earlier post. my bad I set my tension (85 Auto, 32v) pretty much right in the window about a year (and 1500) miles ago and it still reads good.

Fogey1

That's a very reasonable question to ask abot the Kempf tool. Here are a few more:

Was Earl's P-tool calibrated with the bar before and/or after your test and was it right?

Did you try the test in reverse, i.e., tension the timing belt using Jay's tool and then measure with the P-tool?

Since you mention 1/16", did you check any other setting tensions to see if you could establish a consistent relation between P-tool tension readings and Kempf tool readings?

Did you try any other Kempf tools to see if they read the same as the one you mention. I'll volunteer to loan a brand-new (purchased around Christmas), un-used one for this purpose, if you wish.

Thanks for your post.

F451

Yes, you've summarized it much better then I did in my long winded original post. So, really, my bad.

Vilhuer

Here's our findings:

https://rennlist.com/forums/928-forum/127171-928-tool-by-kempf.html#post1218779

Shane

Then you get the same thing Bruce and I got when check the tension on Tims' '88S4. Bruces' being a bit new read higher in the window then mine did, by about 3/32".

blown 87

I have both of them at my shop, the Kemph tool will read about 1/16 on the high side when the belt is set at 5.0 on my 87. at least that is what mine does.

Both are good tools, but if you have both I think you will find you will use the 9201just to double check the kemph tool and to set the final tension.

F451

Great questions. Let me try to answer:

Earl calibrated his P-tool with the bar before we started, and I believe he double checked it during out checkes, but I would have to check with Earl to be sure on whether or not he double checked it once we got started.

No, we didn't do it in reverse.

Yes, we did a number of checks and the relationship between the tools was consistent. When the P-tool read loose, the Kempf read loose. When the P-tool read tight, the Kempf tool read tight, etc.

That is why I'm confident that my Kempf tool is now "calibrated" (at least as much as could be done in a shade tree mechanic sort of way).

In more detail, basically, we measured the original tension on my belt with both tools. Belt was scary loose. Then we tensioned the belt up using the recommended procedure - crank pulley to zero, tension, rotate 270 degrees I think it was, then re-measure, rotate again, re-measure. We did this a number of times until we were satisfied that we got the belt tension just right.

No, we didn't try any other Kempf tools to check, but that would have been interesting to see what they read.

Thanks, but I won't be doing anymore experiments, although that is a good idea. And btw, my Kempf tool was brand new too, and that was the first and only time its been used.

I do need to check the tension on my '85 before I sell it, so perhaps I'll see if any of the local PacNW guys want to stop by with their Kempf tools to see what they read.

I suspect they will all read fairly closely as its a simple device. And I guess there is a certain amount of fudge factor with the tool since so many people have been using them with good results.

blown 87

Damn good write up.
You are 100% correct that the factory tool must be used at the proper place.

F451

Thanks! As I suspected it looks like this has been covered at length before.

RyanPerrella

its been noted that the porsche tool is difficult to get repeatable readings. Leading me to believe its difficult to align properly and if you get different readings everytime you do it then thats not any good either.

The kemph tool is pictured in the porsche workshop manual FWIW. I think Kemph copied the porsche tool and makes them off a porsche design.